(1) Field of the Invention
The present invention pertains to an apparatus that is one part of a conveying system for transferring objects, such as bottles, where the apparatus arranges the objects in layers on a pallet. In particular, the present invention pertains to an apparatus that is employed to palletize objects, where improvements result in more time efficient operation of the apparatus.
(2) Description of the Related Art
Many containers such as bottles, cans, jars, jugs, etc. are packaged on pallets for transportation from a manufacturer to a user of the containers or objects. The pallet loads often include layers of the objects, each separated by a paperboard slipsheet, stacked on top of a pallet constructed of wood. The layers of objects and the slipsheets on which the layers rest are secured on the top surface of the pallet by banding, plastic sheet wrap or by other equivalent methods. The pallet loads facilitate the transportation of a significant number of the objects on each pallet load from the manufacture of the objects, through distribution and ultimately to the end user of the objects.
In many conveyor systems in which objects are loaded onto pallets, the faster the system can operate to load pallets the more cost efficient is its operation. With manual loading of pallets being long recognized as slow and expensive, a number of different types of machines have been developed over time that quickly perform the function of unloading and/or loading pallets. These machines are referred to as depalletizers and/or palletizers in the conveying industry. Examples of these types of machines are described in U.S. Pat. Nos. 2,774,489, 3,780,884; 3,844,422; 3,954,190; 3,974,922; 4,058,225; 4,197,046; 4,214,848, and 4,557,656 the disclosures of all of which are incorporated herein by reference.
FIG. 1 is a schematic representation depicting a palletizer apparatus that comprises many features found in other prior art apparatus. The machine shown in FIG. 1 includes an object infeed section A, an elevator section B, and an object outfeed section C. As stated earlier, machines of this type are known in the prior art and various examples of these machines are disclosed in the above-listed patents. In order to simplify the explanation of the construction and operation of these types of machines the drawing of the machine in FIG. 1 has been simplified, deleting many of the intricate component parts of the machine, examples of which are disclosed in the above-listed patents, that enable the machine to function in the manner to be described. The machine will be described as palletizing objects, in this case plastic blow-molded bottles as shown in FIG. 1. It should be understood that xe2x80x9cobjectsxe2x80x9d is intended to mean any of the various different types of objects that may be transported in pallet loads and is not intended that the interpretation be limited to plastic bottles.
The sections of the machine shown in FIG. 1 are all supported by a framework 10. At the object infeed section A, the framework supports the end of a supply conveyor 12 depicted as a belt and pulley conveyor. However, any other type of known supply conveyor may be employed to transport objects to the machine infeed section A. As depicted in FIG. 1, the supply conveyor 12 has transported a layer of objects into the object infeed section A. Conveyors of palletizers of this type usually have side rails (not shown) and depending, vertically reciprocated gates (not shown) that arrange a plurality of the objects into a generally square grouping that is dimensioned to cover a majority of the load supporting surface of a pallet onto which the objects are to be loaded. The grouping of objects 14 arranged on the supply conveyor 12 will comprise one layer of objects to be loaded onto a pallet by the palletizer. When the supply conveyor 12 has conveyed the grouping of objects 14 into the infeed section A and adjacent the elevator section B, the programmable control unit of the palletizer (CU) controls the motor or drive system M for the supply conveyor 12 to stop the conveyor with the grouping of objects adjacent the elevator section B.
Positioned in the elevator section B is an elevator platform 16 having a drive system M that is controlled by the control unit to move vertically in the elevator section B and, to a limited extent, to move horizontally. The elevator platform 16 is part of a carriage assembly of the palletizer, where the carriage assembly is mounted in the frame 10 and is driven by its drive system to move vertically through the elevator section B. The elevator platform 16, being mounted on the carriage assembly, moves vertically with the carriage assembly through the elevator section B and also moves horizontally to a limited extent relative to the carriage assembly.
A sweeper assembly 18 is also mounted on the carriage assembly for vertical movement with the carriage assembly. In addition, the sweeper mechanism 18 is mounted on the carriage assembly for horizontal movement of the sweeper mechanism 18 across the carriage assembly between the infeed section A, the elevator section B, and the object outfeed section C. Therefore, the sweeper mechanism 18 not only moves vertically with the elevator platform 16 as the carriage assembly moves vertically, but may also move horizontally relative to the elevator platform 16. The sweeper mechanism 18 has a pair of side flaps 22, a front flap 24 and a rear flap 26 mounted for pivoting movement about the top edges of the four flaps. The top edges of the four flaps are suspended from four edges of a base 28 of the sweeper mechanism 18. The base 28 is generally rectangular so that when the four flaps are moved to depend straight downward from the base 28 they define a square that extends around the grouping of objects 14. The pivoting movement of the flaps is controlled by actuators M that are controlled by the control unit of the palletizer to move the pair of side flaps 24 upwardly and move the front 24 and rear 26 flaps upwardly.
An end of an output conveyor 30 is supported in the palletizer frame in the object outfeed section C. The output conveyor 30 in the preferred embodiment is a chain and sprocket conveyor. Conveyors of this type are known in the art and are generally comprised of shafts with two or more sprockets mounted on the shaft in a spaced apart relation. The shafts are positioned parallel to each other in a spaced arrangement along the conveying length of the conveyor. Loops of chain are meshed between the sprockets of adjacent shafts. In prior art FIG. 1, the sprockets 32 and loops of chain 34 are represented schematically. The drive system for the output conveyor 30 is controlled by the control unit to selectively rotate the shafts and their sprockets 32, thereby causing the chains 34 around the sprockets to convey objects, such as the pallet 36 shown in FIG. 1, on the output conveyor 30.
The output conveyor 30 shown in FIG. 1 conveys a pallet 36 loaded with layers of objects 14 out of a loading station 38 in the object outfeed section C of the palletizer. However, before the pallet 36 is loaded with layers of objects by the palletizer, an empty pallet 36, with a slipsheet 40 positioned thereon, must first be moved into the loading station 38 of the outfeed section C. An empty pallet with its slipsheet is usually conveyed into the loading station 38 by a pallet input conveyor (not shown). In the schematic representation of the palletizer shown in FIG. 1, the supply conveyor 12, the elevator platform 16 and the output conveyor 30 are all arranged in a longitudinal line from left to right. The empty pallet input conveyor in systems such as that shown in FIG. 1 is usually positioned to a lateral side of the object outfeed section C so that it will supply an empty pallet and slipsheet in a lateral direction onto the output conveyor 30 at the loading station 38 in the object outfeed section C of the palletizer. As shown in FIG. 1, the pallet input conveyor would be positioned in a perpendicular orientation relative to the output conveyor 30 on either the side of the loading station 38 shown in FIG. 1 or on the opposite side. Therefore, an empty pallet is supplied to the loading station 38 by the pallet input conveyor by being conveyed in a first direction into the loading station 38 and onto the chains 34 of the output conveyor 30, and the loaded pallet is conveyed by the output conveyor 30 in a second direction that is oriented at a right angle to the first conveyor direction of the empty pallet input conveyor.
In the prior art palletizer apparatus shown in FIG. 1, several sensors are mounted at key positions on the palletizer to detect the movement of component parts of the palletizer as well as the empty pallets, layers of objects being loaded onto the pallets, and loaded pallets in controlling the sequential operation of the palletizer. The information determined by these sensors is monitored by the palletizer control unit and the control unit controls the systematic operation of the drive systems of the several palletizer components. Various different types of sensors are employed such as photo sensors and mechanical sensors. The photo sensors are typically photo emitters and reflectors that are mounted on the palletizer spaced from each other. A light beam is emitted by the photo emitter to the photo receptor and the reflection of the light beam is sensed by the photo emitter. However, when the light beam is interrupted by either a component part of the palletizer, a layer of objects being palletized, or a pallet, this interruption is also conveyed to the control unit where the information is employed in controlling the operation of the component parts of the palletizer. The mechanical sensors employed are typically switches that are contacted by a component part of the palletizer or the objects or pallets, which contact activates the switch and sends a signal to the control unit of the palletizer informing the control unit that contact has occurred. The control of palletizers by programmable computerized control units and by sensors such as those discussed above is well known in the prior art and, in order to simplify the description of the improvements provided by the present invention, will only be described generally without going into intricate detail.
The present invention provides improvements to the palletizing apparatus of the prior art described above that enable certain operative sequences of the prior art palletizer to occur quicker, thereby increasing the overall speed by which the palletizer positions an empty pallet into the loading station, loads layers of objects onto the empty pallet in the loading station and then conveys the loaded pallet from the loading station to again restart the sequence by conveying an empty pallet into the loading station. By enabling certain operating sequences of the palletizer to occur in less time, sometimes only reducing the operating time of the sequence by a few seconds, the improvements provided by the present invention can significantly increase the efficiency of operation of the palletizer when the palletizer is operated continuously over an extended period of time, for example an eight hour work shift.
One of the improvements provided by the present invention is made to the empty pallet input conveyor. The empty pallet input conveyor is a sprocket and chain conveyor, similar to the full pallet output conveyor. The empty pallet input conveyor and the full pallet output conveyor intersect each other at right angles. Because these two conveyors intersect, they cannot be operated simultaneously. Furthermore, in the prior art palletizer the empty pallet input conveyor was operated to retract below the level of the conveyor chains of the full pallet output conveyor after an empty pallet had been conveyed into the loading station. With the conveying chains of the full pallet output conveyor positioned above the conveying chains of the empty pallet input conveyor, the output conveyor could be operated to convey a loaded pallet out of the loading station without interference from the chains of the input conveyor. However, once the full pallet left the loading station, the input conveyor would be elevated so that its chains were positioned above those of the output conveyor to enable an empty pallet to be conveyed by the input conveyor into the loading station. However, to avoid interfering with the chains of the full pallet output conveyor conveying a loaded pallet from the loading station, the chains of the empty pallet input conveyor could not be elevated until the loaded pallet had completely cleared the loading station. Therefore, the conveying of an empty pallet into the loading station could not begin to occur until the loaded pallet had completely cleared the loading station.
An improvement provided by the present invention divides the empty pallet input conveyor into first and second sections where the second section intersects with the full pallet output conveyor. The first and second sections of the empty pallet input conveyor could be elevated separately and in sequence with the first section adjacent the full pallet output conveyor being elevated first and the second section intersecting the full pallet output conveyor being elevated sequentially second. This enables the first section of the empty pallet input conveyor to be elevated and the drive system activated to begin conveying an empty pallet toward the loading station of the output conveyor while the output conveyor was still conveying a loaded pallet out of the loading station. This early activation of the empty pallet input conveyor drive system enables an empty pallet to be loaded into the loading station seconds earlier than the prior art empty pallet input conveyor. Over an extended period of time of operation of the palletizing apparatus these saved seconds would amount to a significant savings in time and a more efficient operation of the palletizing apparatus.
In the prior art palletizer the object supply conveyor is elevated slightly above the output conveyor. This relative positioning of the supply and output conveyors would distribute the total range of vertical movement of the elevator platform and the sweeper mechanism below and above the supply conveyor. When initially positioning a first layer of objects to be loaded onto an empty pallet positioned in the loading station of the palletizer, the control unit would first have to determine if an empty pallet was present in the loading station. This was accomplished by a photo sensor in the loading station that would detect a pallet when the pallet was positioned in the loading station. When the elevator mechanism receives a first layer of objects from the supply conveyor by the sweeper mechanism, the downward movement of the elevator mechanism would not commence until the control unit received a signal from the sensor switch in the loading station indicating that an empty pallet was positioned in the loading station. Upon receiving this signal, the control unit would then cause the elevator mechanism drive system to vertically lower the elevator platform until it would contact a mechanical switch at the bottom of the elevator section B indicating that the elevator platform had arrived at the bottom of the elevator section and was adjacent the empty pallet. Therefore, in the prior art palletizer, the downward movement of the elevator mechanism would not commence until the sensor in the loading station communicated to the control unit that an empty pallet was positioned in the loading station.
The present invention adds a second sensor in the form of a mechanical switch in the elevator section B, where the second sensor switch is positioned a short distance vertically above the switch at the bottom of the elevator section that senses when the elevator platform is adjacent the empty pallet. In addition, the control unit is reprogrammed so that, the elevator platform, having a layer of objects swept thereon by the sweeper mechanism, begins its vertically downward movement before the control unit determines the presence or absence of an empty pallet in the loading section. However, when the elevator platform reaches the added sensor switch and trips this switch, the control unit then determines the presence or absence of an empty pallet in the loading section. If the presence of a pallet in the loading section is communicated to the control unit by the sensor in the loading section, then the elevator platform continues with its vertically downward movement until it trips the second, lower switch at the bottom of the elevator section where the elevator platform is positioned adjacent the empty pallet. However, if the elevator platform trips the added switch in the elevator section and the control unit determines that an empty pallet has not yet been loaded into the loading section, then the downward movement of the elevator platform is stopped by the control unit until the control unit receives a signal from the switch in the loading station indicating that an empty pallet has been loaded into the loading station. By adding the additional switch to the elevator section, the elevator platform can begin its downward movement before the control unit determines whether or not an empty pallet is present in the loading station. This modification also results in the savings of small increments of time, for example, seconds. However, when measured over the continuous operation of the palletizer for an extended period of time, for example an 8 hour shift, the savings of time becomes substantial.
Additional time saving improvements are provided on the carriage assembly that supports the elevator platform 16 and the sweeper mechanism 18. In operation of the prior art carriage assembly, after the sweeper mechanism 18 had swept a layer of objects onto the elevator platform 16, the carriage assembly would vertically position the elevator platform adjacent either the empty pallet or a slipsheet covering a layer of objects loaded onto the empty pallet. In positioning the elevator platform 16, the drive system of the carriage assembly would first move the elevator platform 16 horizontally forward toward the loading station so that a forward edge of the elevator platform 16 would slightly overlap the empty pallet or the slipsheet covering a layer of objects on the pallet. The carriage mechanism control system would then control the elevator platform 16 and sweeper mechanism 18 to move downwardly a short distance so that the forward edge of the elevator platform was resting on or just above the empty pallet or slipsheet covering a layer of objects on the pallet. This would ensure that there was not a gap between the forward edge of the elevator platform and the pallet or slipsheet before the sweeper mechanism 18 was controlled to move horizontally to sweep the layer of objects off the elevator platform 16 and onto the pallet or slipsheet.
The present invention improves the operation of the prior art carriage assembly by adding an additional sensor that senses the horizontal position of the sweeper mechanism and allows it to move with the elevator platform when the carriage is moving downward toward the pallet or slipsheet. The control unit controls the drive system of the carriage assembly to move the elevator platform and sweeper mechanism downward as they are continued to move horizontally toward the added horizontal sensor and the pallet or slipsheet. As a result, the sensor mechanism 18 and the elevator platform 16 move diagonally downward and toward the pallet or slipsheet in the improved operation of the carriage assembly instead of moving horizontally toward the pallet or slipsheet and then downwardly toward the pallet or slipsheet. This modification also results in the savings of small increments of time. However, when multiplied over the continuous operation of the palletizer for an extended period of time, the savings of time becomes substantial.
A still further time saving modification of the carriage assembly adds a photo sensor and receptor to the carriage assembly that gives the control unit an early indication that the carriage assembly is about to clear a top layer of objects on a pallet stack when the carriage is moving upwardly. This early indication reduces the time required to reverse the carriage movement from upward movement to downward movement. Again, the modification results in the savings of small increments of time. However, when measured over the continuous operation of the palletizer for an extended period of time, the savings of time becomes substantial.